Screen won't turn on (stays black)

I keep having problems with my HP Pavilion TX 1000 laptop. As I turn on the laptop, all the lights turn on and I hear the computer fan turning on but the screen stays black. I've tried everything (holding power button for 30 sec.; unplugging battery; unplugging power cord; etc.) and nothing works. I don't have an alternate cord to plug into a second computer. I need this computer for school. What can I do?